1. Field of the Invention
The invention relates to methods, apparatus and systems for opposing pressure-induced loads acting upon downhole equipment components. In one embodiment, for example, the invention relates to methods, apparatus and systems capable of at least partially offsetting pressure-induced forces acting upon the mandrel and resulting forces on the shear element of a downhole packer system.
2. Description of Related Art
In the petroleum exploration and recovery industries, equipment used in subsurface wells is often subject to various pressure-induced loads. For example, xe2x80x9cpackersxe2x80x9d are commonly employed in subsurface wells for securing the position of tubing or other equipment in the well, and for zonal isolation to allow various treatments, or operations, to be conducted. A typical packer includes, among other components, a mandrel having a conduit in fluid communication with the tubing, one or more slips that anchor the packer to the wellbore or casing, one or more elastomeric elements that seal the wellbore at the packer, and one or more shear elements to enable emergency unset of the packer, or some combination thereof. The shear element is typically located on the mandrel and engages the mandrel with other packer components.
In use, the typical packer is set at the desired location in the wellbore. A tension-set type packer, for example, is set by applying tension to the tubing on which the packer is conveyed into the wellbore. Such tension is transferred through the mandrel and shear element, such as a shear ring, to the elastomeric element(s) and slip(s), energizing the elastomeric element and forcing the slip into contact with the wellbore wall. In any case, after the packer is set, treating pressure can be applied through the tubing to the isolated wellbore below the packer. The treating pressures cause loads to be placed upon the mandrel, referred to herein as xe2x80x9cpressure-induced forcesxe2x80x9d (F1). Examples of pressure-induced forces may include tubing forces arising from pressure ballooning of the tubing and friction of fluid pumped through the tubing. The pressure-induced forces are transferred from the mandrel through the shear element to the packer""s elastomeric element and slip. Under such forces, the shear element is often forced upwardly into contact with other components of the packer system, imparting shearing loads, or resisting mechanical forces, upon the shear element.
As a result of pressure-induced forces placed upon downhole equipment in the petroleum exploration and recovery industries, limitations are placed upon downhole equipment and/or operations. For example, if the pressure-induced forces upon the shear element of a packer system exceed its shear rating, the shear element may fail. Thus, while the shear element must be designed to fail, or shear, under a certain tension to allow emergency unsetting of the packer, it must also be designed to withstand certain pressure-induced forces to avoid premature or undesirable failure during operations.
Shear elements are often designed with shear ratings sufficient to prevent shearing during normal operations, or to withstand high well treating pressures, but with an emergency unset load that may be greater than the tensile rating of the tubing. Consequently, the tubing or other equipment may fail or become damaged and/or the shear element may not shear as desired to unset the packer.
Further, in some operations, a xe2x80x9cdisconnectxe2x80x9d may be used in conjunction with one or more downhole components, such as a bottom-hole assembly, to allow emergency disconnect of the tubing therefrom. When a packer system is also employed, the disconnect load for the disconnect must be greater than the packer shear element emergency unset load and less than the tubing tensile rating. Consequently, the inclusion of a disconnect further restricts the rating of the packer shear element and, ultimately, the allowable treating pressures during operations.
Thus, there remains a need for methods, apparatus, and/or systems capable of one or more of the following: opposing forces placed upon the shear element of a downhole component; opposing pressure-induced forces placed upon the mandrel of a packer system during use; opposing or balancing mechanical loads placed upon the shear element of a tension-set packer due to pressure-induced forces placed upon the mandrel of a packer system; compensating for upwardly acting, pressure-induced, forces on the mandrel of a packer caused by tubing pressure; opposing the tubing pressure load on a mandrel to reduce the resulting mechanical load on a shear ring of a tension-set packer system; and offsetting the generally upwardly acting mechanical loads on the shear element of a packer resulting from pressure-induced forces on the mandrel of the packer during use.
In accordance with the present invention, certain embodiments involve an apparatus for opposing pressure-induced forces acting upon the mandrel of a packer during use of the packer in a borehole. The packer is in fluid communication with the bore of a tubing. The apparatus includes a piston housing having a cavity and a piston disposed and axially movable within the cavity. The piston is associated with a piston carrier and engageable with the mandrel of the packer. At least one port is disposed in the piston carrier above the piston and capable of allowing pressure communication between the tubing bore and the cavity above the piston, whereby forces placed upon the piston thereby are transferred to the mandrel and capable of at least partially opposing pressure-induced forces acting upon the mandrel.
Forces placed upon the piston and transferred to the mandrel may offset pressure-induced forces acting upon the mandrel. The piston, the piston carrier, and the cavity may be sized to offset the pressure-induced forces acting on the mandrel. Such forces acting on the mandrel are the result of fluid pressure acting on the mandrel cross-section, pressure ballooning or contraction of the tubing, and fluid friction acting on the tubing.
The piston may be located above the packer. At least one hole may be included in the piston housing and extend between the cavity below the piston and the borehole, the hole(s) allowing pressure communication between the borehole and the cavity below the piston.
The packer may be a tension-set packer, which may be deployed on coiled tubing. The packer may be capable of multi-set operation. The packer may include at least one shear element engaged with the mandrel, whereby forces transferred to the mandrel from the piston are applied to the shear element. The shear element(s) may be a shear ring.
In various embodiments, the present invention involves a pressure-compensating apparatus for opposing pressure-induced forces acting generally upwardly upon the mandrel of a tension-set packer during use of the tension-set packer within a borehole. The mandrel is associated with and axially movable relative to a packer housing. The tension-set packer is in fluid communication with the bore of a tubing. A piston is engageable with the mandrel, the piston being driven by pressure communicated from the tubing bore, whereby generally downwardly acting axial forces placed upon the piston from pressure communicated from the tubing bore may be transferred to the mandrel to at least partially oppose pressure-induced forces acting generally upwardly upon the mandrel.
The piston may be disposed and axially movable within a cavity, in which case the mandrel is axially movable relative to the packer housing coincident with the axial movement of the piston within the cavity. The piston may be carried by a piston carrier and at least one port may be disposed in the piston carrier and capable of allowing pressure communication between the tubing bore and the cavity above the piston. The piston and cavity may be disposed in a piston housing and at least one hole may be disposed in the piston housing to extend between the cavity and the borehole, the hole(s) allowing pressure communication between the borehole and the cavity below the piston.
The tension-set packer may be deployed on coiled tubing, and may be capable of multi-set operation. Forces placed upon the piston and transferred to the mandrel may be capable of balancing pressure-induced forces acting upon the mandrel. The piston may be located up-hole of the tension-set packer.
There are yet some embodiments of the invention that involve an apparatus for at least partially reducing mechanical forces acting upon at least one shear ring of a packer system during use of the packer system in a borehole. The shear ring is carried by a mandrel and the mechanical forces acting on the shear ring are caused by pressure-induced forces acting on the mandrel. The packer system is in fluid communication with the bore of a tubing. The apparatus includes a housing having a cavity, and a piston disposed and axially movable within the cavity. The piston is associated with a piston carrier and engageable with the mandrel of the packer system. At least one port is formed in the piston carrier above the piston, the at least one port capable of allowing fluid pressure communication between the tubing bore and the cavity above the piston. Generally downwardly acting forces placed upon the piston by pressure in the cavity are transferred to the mandrel and the at least one shear ring.
The packer system may include a tension-set packer deployed on coiled tubing, and the tension-set packer may be capable of multi-set operation. Generally downwardly acting forces placed upon the piston and transferred to the mandrel may be capable of equalizing pressure-induced forces acting upon the mandrel.
Various embodiments of the invention involve a pressure-balanced, tension-set packer system in fluid communication with the bore of a tubing. The system includes a packer housing, a mandrel associated with and axially movable relative to the packer housing and a piston engageable with the mandrel and carried by a piston carrier. The piston is disposed and axially movable within a cavity. At least one port formed in the piston carrier is capable of allowing pressure communication between the tubing bore and the cavity above the piston, whereby forces placed upon the piston may be transferred to the mandrel, at least partially opposing pressure-induced forces acting upon the mandrel. Forces placed upon the piston and transferred to the mandrel may be capable of balancing pressure-induced forces acting upon the mandrel. The tension-set packer may be capable of multi-set operations and deployed on coiled tubing.
There are yet many embodiments of the invention that involve a method for opposing generally upwardly acting, pressure-induced forces upon the mandrel of a tension-set packer during use of the packer in a borehole. The tension-set packer is in fluid communication with the bore of a tubing. This method includes connecting a piston with the mandrel, deploying the tension-set packer into the borehole, and setting the tension-set packer in the borehole. Generally upwardly acting, pressure-induced forces are allowed to act upon the mandrel, and pressure from the tubing bore is ported to the up-hole side of the piston. Generally downwardly acting forces applied to the piston are transferred to the mandrel, thereby opposing generally upwardly acting, pressure-induced forces upon the mandrel.
Such method may further include disposing the piston within a cavity, associating the piston with a piston carrier and forming a port in the piston carrier to allow the communication of pressure to the cavity above the piston from the tubing bore. If desired, the method may include designing the piston, piston carrier, and cavity so that forces transmitted to the mandrel from the piston will offset generally upwardly acting, pressure-induced forces upon the mandrel. The method may include enabling multi-set operations of the tension-set packer. If desired, the method may be conducted in a non-vertically oriented borehole.
Accordingly, the present invention includes features and advantages that are believed to enable it to advance the technology associated with compensating for pressure-induced forces on downhole equipment. Characteristics and advantages of the present invention described above, as well as additional features and benefits, will be readily apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments and referring to the accompanying drawings.